Suppressing noise in touch panels using a shield layer

ABSTRACT

A method, apparatus, and system measure, at a first channel of a processing device, a first signal indicative of a touch object proximate to an electrode layer. The first signal includes a touch data component and a first noise component generated by a noise source. The method, apparatus, and system measure, at a second channel of the processing device, a second signal including a second noise component generated by the noise source. The second channel is coupled to a shield layer disposed between the noise source and the electrode layer. The method, apparatus, and system generate an estimated noise signal using the second noise component of the second signal that is associated with the second channel. The method, apparatus, and system subtract the estimated noise signal from the measured first signal to obtain the touch data component of the first signal.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional application No.62/557,472, filed Sep. 12, 2017, which is hereby incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to sensing systems, and moreparticularly to capacitance measurement systems configurable to suppressnoise in touch panels using shield layers.

BACKGROUND

Capacitance sensing systems can sense electrical signals generated onelectrodes that reflect changes in capacitance. Such changes incapacitance can indicate a touch event (i.e., the proximity of an objectto particular electrodes). Capacitive sense elements may be used toreplace mechanical buttons, knobs, and other similar mechanical userinterface controls. The use of a capacitive sense element allows for theelimination of complicated mechanical switches and buttons, providingreliable operation under harsh conditions. In addition, capacitive senseelements are widely used in modern consumer applications, providing userinterface options in existing products. Capacitive sense elements canrange from a single button to a large number arranged in the form of acapacitive sense array for a touch-sensing surface of a touch panel.

Capacitive sense arrays and touch buttons are ubiquitous in today'sindustrial and consumer markets. They can be found on cellular phones,GPS devices, set-top boxes, cameras, computer screens, MP3 players,digital tablets, and the like. The capacitive sense arrays work bymeasuring the capacitance of a capacitive sense element and evaluatingfor a delta in capacitance indicating a touch or presence of a touchobject. When a touch object (e.g., a finger, hand, or other conductiveobject) comes into contact or close proximity with a capacitive senseelement, the capacitance changes and the conductive object is detected.The capacitance changes can be measured by an electrical circuit. Theelectrical circuit converts the signals corresponding to measuredcapacitances of the capacitive sense elements into digital values. Themeasured capacitances are generally received as currents or voltagesthat are integrated and converted to the digital values.

There are two typical types of capacitance: 1) mutual capacitance wherethe capacitance-sensing circuit measures a capacitance formed betweentwo electrodes coupled to the capacitance-sensing circuit; 2)self-capacitance where the capacitance-sensing circuit measure acapacitance of one electrode. A touch panel may have a distributed loadof capacitance of both types (1) and (2) and some touch solutions senseboth capacitances either uniquely or in hybrid form with its varioussense modes.

BRIEF DESCRIPTION OF THE DRAWINGS

The present embodiments are illustrated by way of example, and not oflimitation, in the figures of the accompanying drawings.

FIG. 1 is a block diagram illustrating a touch panel stack up, inaccordance with aspects of the disclosure.

FIG. 2 is a block diagram illustrating system to suppress noise of atouch panel, in accordance with aspects of the disclosure.

FIG. 3 is a block diagram illustrating a system to suppress noise of atouch panel and includes a circuit model of the touch panel stack-up, inaccordance with aspects of the disclosure.

FIG. 4 is a block diagram illustrating a system to suppress noise of atouch panel with an alternative circuit implementation, in accordancewith aspects of the disclosure.

FIG. 5 is a block diagram illustrating a system to suppress noise of atouch panel including a filter, in accordance with aspects of thedisclosure.

FIG. 6 is a block diagram illustrating the path of the noise signal in asystem to suppress noise of a touch panel, in accordance with aspects ofthe disclosure.

FIG. 7 is a block diagram illustrating a system to suppress noise of atouch panel with a filter in an alternative circuit implementation, inaccordance with aspects of the disclosure

FIG. 8 is a block diagram illustrating a system to suppress noise of atouch panel with an alternative hardware circuit implementation, inaccordance with aspects of the disclosure.

FIG. 9 is a block diagram illustrating a system to suppress noise of atouch panel with another alternative circuit implementation, inaccordance with aspects of the disclosure.

FIG. 10 is a block diagram illustrating a system to suppress noise of atouch panel with an alternative circuit implementation, in accordancewith aspects of the disclosure.

FIG. 11 is a flow diagram illustrating method for suppressing a noisesignal from a touch panel, in accordance with aspects of the disclosure.

FIG. 12 is a flow diagram illustrating method for determining anattenuation coefficient used to generate the estimated noise signal, inaccordance with aspects of the disclosure.

FIG. 13 is a block diagram illustrating an electronic system thatprocesses touch data, in accordance with aspects of the disclosure.

FIG. 14 illustrates an embodiment of a core architecture of theProgrammable System-on-Chip (PSoC®) processing device, in accordancewith aspects of the disclosure.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present embodiments. It will be evident, however,to one skilled in the art that the present embodiments may be practicedwithout these specific details. In other instances, well-known circuits,structures, and techniques are not shown in detail, but rather in ablock diagram in order to avoid unnecessarily obscuring an understandingof this description.

Reference in the description to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least oneembodiment. The phrase “in one embodiment” located in various places inthis description does not necessarily refer to the same embodiment.

In some touch sensing systems, such as capacitive touch sensing systems,a noise source of a touch panel may generate noise signals thatinterfere with the detection of a touch object proximate the touchpanel. For example, an electrode layer (also referred to as a “sensearray” herein) may be disposed above a display device, such as a liquidcrystal display of a touch panel. A noise signal from the operation ofthe display device may couple to the electrode layer via parasiticcapacitive coupling. The coupled noise signal may interfere with themeasuring signal (e.g., a transmission (Tx) signal) at the electrodelayer used to detect a touch object proximate the electrode layer.

In some touch sensing systems, a shield layer disposed between theelectrode layer and display device is used to help shield the electrodelayer from the noise signal generated by the display device. The shieldlayer may be coupled to a ground potential. However, the shield layerhas sheet resistance that creates a voltage potential in the presence ofthe noise signal. Thus, the noise signal is coupled to the electrodelayer via parasitic capacitive coupling between the electrode layer andshield layer, which obscures with the measuring signal used to detect atouch object.

Some touch sensing systems, may use a first electrode of the electrodelayer to sample the noise signal. After sampling the noise signal, asecond different electrode (or same electrode) may be used tosubsequently measure a touch using a measuring signal. The sampled noisesignal from the first electrode may be used to reduce the noise from themeasuring signal measured at the second electrode. However such systemsmay suffer from linearity and accuracy degradation. Such systems may behighly sensitive to a touch by a touch object. Sampling and measuringmay be performed sequentially for systems that are highly sensitive to atouch. For example, if the above system concurrently measures the firstelectrode for the noise signal and the second electrode for themeasuring signal, the first electrode samples a large amount of themeasuring signal and the touch data associated therein. Using the signalfrom the first electrode, which includes a large amount of the measuringsignal, to reduce the noise of the measuring signal of the secondelectrode eliminates a large portion of the usable data (e.g., touchdata) from the measuring signal leading to inaccurate touchmeasurements.

Aspects of the disclosure address the above and other challenges bymeasuring, at a first channel of a processing device, a first signalindicative of a touch object proximate to an electrode layer. A channelmay refer to hardware, firmware, software, or combination thereof use toreceive, manipulate, or measure a received signal. The first channel iscoupled to the electrode layer. The first signal includes a touch datacomponent and a first noise component generated by a noise source. Thesecond channel of the processing device measures a second signalincluding a second noise component generated by the noise source. Thesecond channel is coupled to a shield layer disposed between the noisesource and the electrode layer. An estimated noise signal is generatedusing the second noise component of the second signal that is associatedwith the second channel. The estimated noise signal is an estimation ofthe first noise component of the first signal. The estimated noisesignal is subtracted from the measured first signal to obtain the touchdata component of the first signal. In an embodiment, measuring thefirst signal at the first channel is performed concurrently with themeasuring of the second signal.

The noise signal sampled at the shield layer includes a negligibleamount of the measuring signal because the shield layer is further awayfrom the touch object, is partially shielded by the above electrodelayer. The measuring signal that is injected from the electrode layer tothe shield layer may be significantly attenuated (e.g., by an order ofmagnitude). This reduces the amount of the measuring signal (and touchdata component therein) that is coupled to the shield layer and sampleda the second channel. The signal obtained from the shield layer can beused to reduce the noise from the measuring signal without significantlyimpacting the usable touch data of the measuring signal.

Aspects of the disclosure may be applied to self-capacitance measuringtechniques or mutual capacitance measuring techniques.

FIG. 1 is a block diagram illustrating a touch panel stack up, inaccordance with aspects of the disclosure. System 100 shows a touchpanel stack-up 101 that illustrates various layers that are included ina touch panel. A touch panel may display images and video to users andbe included in various electronic devices, such as mobile devices orfront panel displays. A touch panel may also be used in conjunction withprocessing device 116 to detect a touch (also referred to as a “touchevent”) by a touch object 102 (e.g., a human finger or other touchobject) proximate to the touch panel. For example, a touch by touchobject 102 in physical contact with overlay may be detected. In anotherexample, a touch by touch object some distance above overlay 104 (e.g.,hovering approximately 35 millimeters (mm) above overlay 104) may alsobe detected. It can be noted that a touch object proximate the touchpanel may be detected at distances greater than 35 mm using aspects ofthe present disclosure.

In an embodiment, the touch panel stack-up 101 may include one or moreof an overlay 104, an electrode layer 106, a shield layer 108 or a noisesource 112. As illustrated, each of the aforementioned layers may bedisposed above the subsequently mentioned layer(s). For example, theoverlay 104 is disposed above electrode layer 106, shield layer 108, andnoise source 112. In another example, shield layer 108 may be disposedbetween the electrode layer 106 and noise source 112.

In an embodiment, overlay 104 may be a transparent or semi-transparentmaterial that is disposed above the electrode layer 106. The overlay 104may provide protection or other functionality, such as filtering, to theunderlying layers.

In an embodiment, the electrode layer 106 (also referred to as a “sensearray” herein) includes one or more electrodes. In an embodiment, theelectrode layer 106 may be a capacitive sense array. For purposes ofillustration, rather than limitation, touch panel stack-up 101 isillustrated with a single electrode (i.e., a receiving (Rx) electrode).If can be appreciated that the electrode layer 106 may include manyelectrodes, such as multiple transmission (Tx) electrodes and multipleRx electrodes. The electrode layer 106 can be used to sense touch object102 proximate to the electrode layer 106. For example, in mutualcapacitance mode a Tx signal may be generated and coupled to a Txelectrode. From the Tx electrode the Tx signal may be capacitivelycoupled to a respective Rx electrode. A change in the capacitancebetween the Tx electrode and respective Rx electrode is measured (e.g.,the measuring signal) at the Rx electrode of electrode layer 106 in thepresence of a touch object 102. The measuring signal may include a touchdata component indicative of a touch object 102 proximate to the Rxelectrode of electrode layer 106. In mutual capacitance mode, themeasuring signal may be an induced current at the Rx electrode caused bythe Tx signal from the respective Tx electrode. In another example, inself-capacitance mode an Rx electrode can be excited using an excitationsignal (e.g., by varying the ground potential). A touch object proximatethe Rx electrode can capacitively couple with the respective Rxelectrode and change the capacitance sensed at the Rx electrode. Achange in the capacitance at the Rx electrode (e.g., from having notouch object proximate the Rx electrode to having a touch objectproximate the Rx electrode) can be measured using the measuring signal.The measuring signal may include a touch data component indicated of atouch object 102 proximate to the Rx electrode of the electrode layer.In self-capacitace mode, the measuring signal may be an induced signalat the Rx electrode caused by the excitation signal.

In embodiments, the electrode layer 106 may be a transparent orsemi-transparent conductive material, such as indium tin oxide (ITO).Electrode layer 106 (i.e., sense array) and touch detection is furtherdescribed with respect to FIG. 11.

In an embodiment, the shield layer 108 may be used to help shieldelectrode layer 106 from parasitic noise signals. For example, noisefrom noise source 112 may be injected into the electrode layer 106 viaparasitic capacitive coupling. The noise that is injected into theelectrode layer 106 by noise source 112 may be combined with a measuringsignal that includes touch data and decrease the accuracy of touchdetection. A shield layer 108 may be used to help de-couple one or morenoise sources, such as noise source 112, from the electrode layer 106and increase the accuracy of a measuring signal. In the current example,shield layer 108 is coupled to system ground 114, which may refer to theground potential of the device in which the touch panel stack-up 101 isimplemented. For example, in a mobile device the system ground 114 maybe battery of the mobile device. In embodiments, the shield layer 108may be a transparent or semi-transparent conductive material. Thematerial of the shield layer may be a similar material as described withrespect to electrode layer 106. For example, the shield layer mayinclude indium tin oxide (ITO). In an embodiment, the shield layer 108is a contiguous, planar, and conductive material.

In an embodiment, the noise source 112 is disposed below the shieldlayer 108. In an embodiment, the noise source 112 may generate a noisesignal, as illustrated by noise signal 126. The noise signal 126generated by noise source 112 may be injected into the shield layer 108and the electrode layer 106 via parasitic coupling. For example, a firstnoise component of noise signal 126 may be injected into the electrodelayer 106 (e.g., the Rx electrode) and a second noise component of thenoise signal 126 may be injected into the shield layer 108. The noisesignal 126 may include both the first noise component and the secondnoise component. The first and second noise components may beproportional to one another. The property of proportionality of thefirst and second noise components of the noise signal 126 may be used tohelp cancel the first noise component received at the Rx electrode, asillustrated below and in aspects of the disclosure.

In an embodiment, a measuring signal is measured by an Rx channel, suchas channel 124A. The injected noise signal 126 may become a part of themeasuring signal, e.g., noise component of the measuring signal. Themeasuring signal may also include a touch data component (e.g., avoltage or current indicating a change in capacitance), which may beobscured by the noise signal and lead to decreased accuracy in touchdetection.

In some embodiments, the noise source 112 may include a display device,such as a liquid crystal display (LCD). In other embodiments, thedisplay device may be a different type of display, such as an organiclight emitting diode (OLED) display or other type of display device.

In an embodiment, the electrode layer 106 is coupled to processingdevice 116. Processing device 116 may measure signal changes, such ascapacitance changes, of electrode layer 106 and produce digital outputs(also referred to as “counts” or “digital counts” herein) indicative ofa touch proximate to a touch panel. In an embodiment, each Rx electrodemay be coupled to a separate channel 124A-124N of processing device 116.It can be noted that in other embodiments, a channel may be coupled tomore than one Rx electrode at a single instance in time. In still otherembodiments, a channel may couple to multiple Rx electrodes but only toone Rx electrode at a particular time (e.g., via a multiplexer).

In an embodiment, a channel, such as channel 124A, may include hardwareor firmware to measure a signal, such as a measuring signal, receivedfrom the respective Rx electrode of electrode layer 106. For example,the measuring signal may be received by a buffer 118. The buffer maybuffer or amplify the received measuring signal. In an embodiment, thebuffer 118 may be a unity-gain buffer. In other embodiments, the buffer118 may have some amount of gain. In an embodiment, the positiveterminal of buffer 118 may be connected to the output of buffer 118. Thenegative terminal of buffer 118 may be coupled to a reference voltage.In other embodiments, a buffer with different configurations may beimplemented.

In an embodiment, the buffered measuring signal at the output of buffer118 may be integrated by integrator 120. Integrator 120 may integratethe buffered measuring signal to combine the buffered measuring signalto produce a raw measuring signal. In an embodiment, the integratedmeasuring signal is an analog voltage or current. In one embodiment, themeasuring signal may include a current (e.g., charge) that is integrated(e.g., accumulate the charge) on a capacitor. The integrated current canbe detected as a voltage change. In embodiments, integrator 120 may be ahardware circuit, firmware, or a combination thereof. In someembodiments, a particular channel 124A-124N may include the same,different, more, or fewer components in different or the sameconfiguration as illustrated in FIG. 1. It can be noted that thecomponents illustrated with respect to channel 124A are provided forpurposes of illustration, rather than limitation.

FIG. 2 is a block diagram illustrating system 200 to suppress noise of atouch panel, in accordance with aspects of the disclosure. Components ofFIG. 1 are used to help describe aspects of FIG. 2. FIG. 2 shows thetouch panel stack-up 101 as illustrated in FIG. 1. Channel 224A and thecomponents therein may be similar to channel 124A of FIG. 1. Buffer 218Aand 218B may be similar to buffer 118 of FIG. 1. Integrator 220A and220B may be similar to integrator 120 of FIG. 1.

As shown in FIG. 2, Rx electrode of electrode layer 106 is coupled tochannel 224A and shield layer 108 is coupled to channel 224B. Bothchannels 224A and 224B are part of processing device 116. In anembodiment, channel 224A and channel 224B (generally referred to as“channel(s) 224” herein) are physically separate channels (e.g., coupledto two distinct output pins of processing device 116). Each channel 224may include its own hardware. In an embodiment, different channels maybe coupled to single pin of the processing device 116 at differentinstances in time using for example, a switch or multiplexer. Forexample, the shield layer 108 can be coupled to channel 224B duringtimes when reducing the touch panel noise from the measuring signal isdetermined to be important. At other times, channel 224B can be coupledto an Rx electrode of the electrode layer 106 to measure a respectivemeasuring signal.

The output of integrator 220B of the channel 224B is coupled to theinput of attenuator 230. The output of attenuator 230 is coupled to asubtraction module 228 capable of subtracting one signal from anothersignal. In embodiments, attenuator 230 may include an attenuatorcircuit, firmware, or a combination thereof. In embodiments, subtractionmodule 228, may include circuitry, firmware, or a combination thereof.In an embodiment, attenuator 230 or subtraction module 228 is part of achannel 224A or 224B. In other embodiments, attenuator 230 orsubtraction module 228 may be outside channels 224.

Noise signal 126 is coupled to both the shield layer 108 and the Rxelectrode of the electrode layer 106. The coupled noise signal 126 isillustrated having a first noise component 232A coupled to the Rxelectrode of electrode layer 106 and a second noise component 232Bcoupled to the shield layer 108. First noise component 232A is coupledto channel 224A and second noise component 232B is coupled to 224B.

In an embodiment, a measuring signal 234 is received at channel 224A.The measuring signal 234 may be indicative of a touch by touch object102 proximate to the electrode layer 106. The measuring signal 234 mayinclude a touch data component indicative of a touch proximate to theelectrode layer 106 and a first noise component 232A. For example, in amutual capacitance implementation a Tx transmission signal may betransmitted to a Tx electrode. The presence of touch object 102 changesthe capacitance between the Tx electrode and the respective Rx electrodeof electrode layer 106. The information of the change in capacitance isincluded in the touch data component of the measuring signal 234. Thenoise component 232A injected by the noise source 112 is also coupled tothe Rx electrode of the electrode layer 106 and included in themeasuring signal 234.

In an embodiment, a shield signal 236 is received at channel 224B. Theshield signal 236 can include the second noise component 232B.

In an embodiment, the measuring signal 234 is measured at channel 224Aof processing device 116. In an embodiment, the measuring can includebuffering the measuring signal 234 at buffer 218A and integrating thebuffered measuring signal at integrator 220A, as further described withrespect to FIG. 1.

In an embodiment, the shield signal 236 that includes the second noisecomponent 232B is measured at channel 224B of processing device 116. Inan embodiment, the measuring can include buffering the shield signal 236at buffer 218B and integrating the buffered shield signal at integrator220B.

In an embodiment, processing device 116 may generate an estimated noisesignal using the second noise component 232B of the shield signal 236.The estimated noise signal may be an estimation of the first noisecomponent 232A of the measuring signal 234 received at channel 224A. Inan embodiment, generating the estimated noise signal using the secondnoise component 232B of the shield signal 236 includes multiplying theshield signal 236 (e.g., the integrated shield signal) at an attenuator230 by an attenuation coefficient (K). It can be noted that anattenuation coefficient may be any real number. Attenuation may includereducing a signal, amplifying a signal, or buffering a signal (e.g.,attenuation coefficient of 1).

In an embodiment, the estimated noise signal may be subtracted from themeasuring signal 234 (e.g., the integrated measuring signal) bysubtraction module 228.

For example, the second noise component 232B may be proportional to thefirst noise component 232A of the noise signal 126. As such, the shieldsignal 236 (e.g., integrated shield signal) that includes the secondnoise component 232B may be attenuated (or amplified) by an attenuationcoefficient (K) to generate an estimated noise signal. The estimatednoise signal may be attenuated so that the estimated noise signal may besimilar in magnitude as the first noise component 232A of the measuringsignal 234 received at channel 224A. The estimated noise signal can besubtracted from the measuring signal 234 to remove or reduce the firstnoise component 232A of the measuring signal 234. The remaining touchdata component of the measuring signal 234 can be used to detect a touchproximate to the electrode layer 106. The above operations can beperformed in the presence of a touch object proximate the touch panel orwith no touch object present.

FIG. 3 is a block diagram illustrating a system 300 to suppress noise ofa touch panel and includes a circuit model of the touch panel stack-up,in accordance with aspects of the disclosure. Components of FIGS. 1 and2 are used to help describe aspects of FIG. 3. FIG. 3 illustrates acircuit model of touch panel stack-up 101. Rx electrode of electrodelayer 106 is represented by multiple resistors (R_(IX)) coupled inseries to channel 224A of processing device 116. The shield layer 108 isrepresented by multiple resistors (R_(s)) coupled in series to channel224B of processing device 116. Coupling capacitors 336 (C_(s2n))represent the parasitic capacitive coupling between the shield layer 108and the noise source 112. Coupling capacitors 334 (C_(rx2s)) representthe parasitic capacitive coupling between the Rx electrode of theelectrode layer 106 and the shield layer 108.

FIG. 4 is a block diagram illustrating a system 400 to suppress noise ofa touch panel with an alternative circuit implementation, in accordancewith aspects of the disclosure. Components of FIGS. 1 and 2 are used tohelp describe aspects of FIG. 4. Integrator 420A and 420B may be similarto integrator 120 of FIG. 1.

Channel 424A and channel 424B may each include integrator 420A andintegrator 420B, respectively. Integrator 420A and 420B may be similarto integrator 120 of FIG. 1. Channel 424A and channel 424B (generallyreferred to as “channel(s) 424” herein) may each include ananalog-to-digital converter (ADC) 438A and 438B, respectively (generallyreferred to as “ADC(s) 438” herein). The ADC 438 may convert an analogsignal into an equivalent digital signal. For example, measuring signal234 at channel 224A may be integrated by integrator 420A. The integratedmeasuring signal 234 maybe converted from an analog signal to a digitalsignal by ADC 438A. Similarly, the shield signal 236 at channel 224B maybe integrated by integrator 420A. The integrated shield signal 236 maybe converted from an analog signal to a digital signal by ADC 438B.

System 400 may provide similar noise suppression as described withrespect to the previous figures. In an embodiment, the digital shieldsignal 236 may be attenuated by attenuator 230. The attenuated digitalshield signal 236 may be subtracted from digital measuring signal 234using subtraction module 228. In an embodiment, attenuator 230 orsubtraction module 228 is part of a channel 424A or 424B. In otherembodiments, attenuator 230 or subtraction module 228 may be outsidechannels 424.

FIG. 5 is a block diagram illustrating a system 500 to suppress noise ofa touch panel including a filter, in accordance with aspects of thedisclosure. Components of FIG. 1-4 are used to help describe aspects ofFIG. 5. It can be noted that any unlabeled components may be similar totheir labelled counterparts in previous Figures.

In an embodiment, system 500 may implement a filter 540 between theshield layer 108 and the input of buffer 218B. The filter 540 may beused to create a similar transfer function between the first noisecomponent 232A of the measuring signal 234 and the second noisecomponent 232B of the shield signal 236, as will be further describedwith respect to FIG. 6.

In an embodiment, filter 540 may include a capacitor 541 (C_(f)) coupledin series with channel 224B and the shield layer 108. In an embodiment,filter 540 may include a resistor 542 (R_(f)). Resistor 542 may includea first terminal coupled between the shield layer 108 and channel 224B.Resistor 542 may include a second terminal coupled to a groundpotential, such as system ground 114. In an embodiment, the filter 540includes both the capacitor 541 and the resistor 542. In an embodiment,one or more of capacitor 541 and resistor 542 are implemented asdiscrete components outside of processing device 116. In anotherembodiment, one or more of capacitor 541 and resistor 542 are integratedas on-chip components of processing device 116.

In an embodiment, resistor 544A (R_(i)) may be coupled between the Rxelectrode of electrode layer 106 and buffer 218A. In an embodiment,resistor 544B (R_(i)) may be coupled between the shield layer 108 andthe input of buffer 218B. In embodiments, one or more resistor 544A and544B (generally referred to as “resistor(s) 544”) may be off-chip oron-chip components. Resistors 544 may assist with immunity, such astransient immunity or radio-frequency immunity.

It can be noted that one or more channels may have similar immunityresistors. For example, each channel may have a similar immunityresistor coupled between the respective Rx electrode of the electrodelayer 106 and the respective channel of processing device 116.

FIG. 6 is a block diagram illustrating the path of the noise signal in asystem 600 to suppress noise of a touch panel, in accordance withaspects of the disclosure. Components of FIG. 1-5 are used to helpdescribe aspects of FIG. 6. It can be noted that any unlabeledcomponents may be similar to their labelled counterparts in previousFigures.

In FIG. 6, the noise signal 126 of noise source 112 is shown propagatingthrough system 600. Signal waveforms 644A-644E (generally referred to as“signal waveform(s) 644” herein) show noise signal 126 or noisecomponents thereof at different nodes (e.g., nodes A-E) in system 600.It can be noted that the signal waveforms are provided for illustration,rather than limitation. Other signal waveform may be present indifferent applications.

At node A, the noise signal 126 is shown as series of triangularwaveforms as illustrated by signal waveform 644A. Noise signal 126propagates from node A to node B via a coupling capacitance 336 betweenthe shield layer 108 and noise source 112.

From node A to node B, the noise signal 126 changes shape (e.g.,. phasechange) as illustrated by signal waveform 644B. The shape change may becaused by coupling capacitance 336 between the shield layer 108 andnoise source 112. From node B, the noise signal 126 propagates to bothnode C and node D.

From node B to node C, the noise signal 126 is slightly attenuated bythe resistance of shield layer 108 as shown by signal waveform 644C.

From node B to node D, the noise signal 126 (e.g. first noise component232A of the noise signal 126) is coupled to the Rx electrode of theelectrode layer 106 via a coupling capacitance 334 between the Rxelectrode of the electrode layer 106 and the shield layer 108. From nodeB to D, the noise signal 126 undergoes another transition (e.g., phasechange) as illustrated by signal waveform 644D.

From node C to node E, the inclusion of capacitor 541 shapes the noisesignal 126 at node E (e.g., second noise component 232B of noise signal126) to be similar in shape as the noise signal 126 at node D (asillustrated by signal waveform 644E and 644D). The second noisecomponent 232B noise signal 126 having the shape of signal waveform 644Ecan be attenuated by a particular attenuation coefficient at attenuator230, and can be subtracted from the first noise component 232A of noisesignal 126 having the shape of signal waveform 644D.

FIG. 7 is a block diagram illustrating a system 700 to suppress noise ofa touch panel with a filter in an alternative circuit implementation, inaccordance with aspects of the disclosure. Components of FIG. 1-6 areused to help describe aspects of FIG. 7. It can be noted that anyunlabeled components may be similar to their labelled counterparts inprevious Figures. Components of FIG. 7 may be similar to components ofFIG. 4. A filter 740 may be included and be similar to filter 540 ofFIG. 5.

FIG. 8 is a block diagram illustrating a system 700 to suppress noise ofa touch panel with an alternative hardware circuit implementation, inaccordance with aspects of the disclosure. Components of FIG. 1-7 areused to help describe aspects of FIG. 8. It can be noted that anyunlabeled components may be similar to their labelled counterparts inprevious Figures.

In an embodiment, a compensation circuit 850 can be used to minimize thenoise injected into a channel, such as channel 224A of processing device116. In an embodiment, the compensation circuit 850 can sample the firstnoise component 232A at the input of buffer 218A. The compensationcircuit 850 may filter the first noise component 232A using filter 840,and invert the filtered first noise component 232A using invertor 852,and inject the inverted first noise component 232A into the shield layer108 using invertor 852, which may reduce the noise component received atthe channel 224A.

In an embodiment, one or more components of compensation circuit 850 areoff-chip components outside the processing device 116 (as illustrated).In another embodiment, one or more components of compensation circuit850 are on-chip components of the processing device 116. In anembodiment, the compensation circuit 850 includes circuit hardwarecomponents. It can be noted that compensation circuit 850 may includethe same, more, less, or different components configured in the same ordifferent configuration in some embodiments.

FIG. 9 is a block diagram illustrating a system 900 to suppress noise ofa touch panel with another alternative circuit implementation, inaccordance with aspects of the disclosure. Components of FIG. 1-8 areused to help describe aspects of FIG. 9. It can be noted that anyunlabeled components may be similar to their labelled counterparts inprevious Figures. System 900 of FIG. 9 is similar to system 400 andsystem 700 of FIG. 4 and FIG. 7, respectively.

In an embodiment, system implements a compensation circuit 950.Compensation circuit 950 performs operations similar to compensationcircuit 850 of FIG. 8. In an embodiment, a compensation circuit 950 canbe used to minimize the noise injected into a channel, such as channel224A of processing device 116. In an embodiment, the compensationcircuit 950 can sample the first noise component 232A at the input ofbuffer 218A. The compensation circuit 850 may filter the first noisecomponent 232A using filter 940, invert the filtered first noisecomponent 232A using an invertor 952, and inject the inverted firstnoise component 232A into the shield layer 108, which may reduce thenoise signal received at channel 224A.

In an embodiment, one or more components of compensation circuit 950 areoff-chip components outside the processing device 116 (as illustrated).In another embodiment, one or more components of compensation circuit950 are on-chip components of the processing device 116. It can be notedthat compensation circuit 950 may include the same, more, less, ordifferent components configured in the same or different configurationin some embodiments. In embodiments one or more components ofcompensation circuit may be implemented in hardware, firmware, or acombination thereof

FIG. 10 is a block diagram illustrating a system 1000 to suppress noiseof a touch panel with an alternative circuit implementation, inaccordance with aspects of the disclosure. Components of FIG. 1-9 areused to help describe aspects of FIG. 10. It can be noted that anyunlabeled components may be similar to their labelled counterparts inprevious Figures.

In system 1000, the noise suppression may be performed at a singlechannel, such as channel 224A. For example, the measuring signal 234having a first noise component 232A may be provided at a first input ofbuffer 218A. The shield signal 236 may be filtered by filter 540 andattenuated by attenuator 1030. The attenuated shield signal 236 isprovided to a second input of buffer 218A, which may allow the buffer218A to effectively filter the first noise component 232A (e.g.,common-mode rejection) from measuring signal 234. The buffered measuringsignal 234 is then integrated at integrator 220.

In an embodiment, attenuator 1030 is a hardware integrator andintegrated into channel 224A of processing device.

FIG. 11 is a flow diagram illustrating method 1100 for suppressing anoise signal from a touch panel, in accordance with aspects of thedisclosure. Method 1100 may be performed by processing logic thatincludes hardware (e.g., circuitry, dedicated logic, programmable logic,microcode), software (e.g., instructions run on a processing device toperform hardware simulation), or a combination thereof. In otherimplementations, noise suppression module 1320 of FIG. 13 can performsome or all the operations. Components of the preceding Figures may beused to help illustrate method 1100. It may be noted that the in someimplementations, method 1100 may include the same, different, fewer, orgreater number of operations performed in any order.

At block 1102, processing logic measures, at channel 224A of aprocessing device 116, a first signal (e.g., measuring signal 234)indicative of a touch object proximate to an electrode layer 106. Thefirst signal includes a touch data component and a first noise component232A generated by a noise source 112.

In an embodiment, measuring the first signal includes buffering thefirst signal using buffer 218A of channel 224A and integrating thebuffered first signal using an integrator 220A.

In another embodiment, measuring the first signal includes integratingthe first signal using integrator 420A and converting the first signalinto a digital signal using ADC 438A.

At block 1104, processing logic measures, at channel 224B of theprocessing device 116, a second signal (e.g., shield signal 236)including a second noise component 232B generated by the noise source112. The channel 224B is coupled to shield layer 108 that is disposedbetween the noise source 112 and electrode layer 106.

In an embodiment, measuring the second signal includes buffering thesecond signal using buffer 218B of channel 224B and integrating thebuffered second signal using an integrator 220B.

In another embodiment, measuring the second signal includes integratingthe second signal using integrator 420B and converting the second signalinto a digital signal using ADC 438B.

In an embodiment, the measuring the first signal at channel 224A isperformed concurrently with measuring the second signal at channel 224B.

At block 1106, processing logic generates an estimated noise signalusing the second noise component 232B of the second signal that isassociated with the channel 224B. The estimated noise signal is anestimation of the first noise component 232A of the first signal.

In an embodiment, generating the estimated noise signal includesattenuating the second signal (e.g., shield signal 236) by anattenuation coefficient to generate the estimated noise signal. Forexample, after the second signal is measured (e.g., buffered andintegrated), the second signal can be attenuated by attenuator 230.

At block 1108, processing logic may subtract the estimated noise signalfrom the measured first signal to obtain the touch data component of thefirst signal. For example, a subtraction module 228 may be used tosubtract the estimated noise signal from the measured first signal. Inan embodiment, the touch data may be used to determine whether a touchby a touch object 102 occurred proximate to an Rx electrode of theelectrode layer 106.

As noted above, similar operations may be used for other channelsassociated with other Rx electrodes of electrode layer 106. Inembodiments, channel 224A may be used to suppress noise for one or morechannels associated with Rx electrodes.

FIG. 12 is a flow diagram illustrating method 1200 for determining anattenuation coefficient used to generate the estimated noise signal, inaccordance with aspects of the disclosure. Method 1200 may be performedby processing logic that includes hardware (e.g., circuitry, dedicatedlogic, programmable logic, microcode), software (e.g., instructions runon a processing device to perform hardware simulation), or a combinationthereof. In other implementations, noise suppression module 1320 of FIG.13 can perform some or all the operations. Components of the precedingFigures may be used to help illustrate method 1200. It may be noted thatthe in some implementations, method 1200 may include the same,different, fewer, or greater number of operations performed in anyorder.

At block 1202, processing logic determines that the noise source 112 ispowered on. For example, the processing device 116 may send a signalthat turns the display device on. In another example, the processingdevice 116 received an indication that the display device is powered on,but may not directly control the display device.

At block 1204, processing logic may turn off one or more excitationvoltages associated with the electrode layer 106. For example, in mutualcapacitance sensing the Tx excitation voltages may be removed. Inanother example, in self-capacitance sensing the excitation voltage maybe turned off by, for instance, coupling the device ground of theprocessing device 116 to the system ground used by the noise source 112.In an embodiment, the excitation voltages are turned off so that a touchdoes not interfere with measurements of the noise signal 126 at bothchannel 224A and channel 224B of processing device 116.

At block 1206, processing logic sets the attenuation coefficient to apredetermined number. For example, the attenuation coefficient ofattenuator 230 may be set to the 1, so that the attenuator 230 buffersthe second noise component (I2) 232B of the noise source 112.

At block 1208, processing logic measures, at the channel 224A ofprocessing device 116, the third signal including the third noisecomponent (e.g., similar to first noise component 232A). In anembodiment, the measurement of the third signal may be similar tomeasurement of the first signal (e.g., measuring signal 234) asdescribed above except that the third signal does not include a touchdata component because the excitation signal is turned off.

At block 1208, processing logic measures at the channel 224B ofprocessing device 116, the fourth signal including the fourth noisecomponent (e.g., similar to second noise component 232B). In anembodiment, the measurement of the fourth signal may be similar tomeasurement of the second signal (e.g., shield signal 236) as describedabove.

In an embodiment, the third signal and the fourth signal are measuredconcurrently.

At block 1210, processing logic estimates the attenuation coefficientusing the third signal and fourth signal from channel 224A and channel224B, respectively. For example, the third signal represents the noisecomponent (e.g., first noise component 232A) of the noise source 112received by the channel 224A. The fourth signal represents the noisecomponent (e.g., second noise component 232B) of the noise source 112received by the channel 224B. Since the excitation signal is turned off,the signals received by channel 224A and channel 224B may berepresentative of the noise source 112 without interference from signalsrepresentative of touch data.

In one embodiment, the attenuation coefficient may be estimated using aratio of the third signal (e.g., first noise component 232A) received atchannel 224A and the fourth signal (e.g., second noise component 232B)received at channel 224B. In another embodiment, the attenuationcoefficient can be estimated using a least square method approach usingthe third signal and the fourth signal.

In an embodiment, the attenuator, such as attenuator 230 or attenuator1030, may be set using the estimated attenuation coefficient.

In an embodiment, determining the attenuation coefficient can beperformed once, for example, after manufacture of the system (e.g.,mobile device). In another embodiment, determining the attenuationcoefficient may be performed more than once, for example periodicallybased on time, number of on-off cycles of the system, or other criteria.In an embodiment, determining the attenuation coefficient can beperformed dynamically, for example when a user is using the system.

In another embodiment, the attenuation coefficient can be determinedbased on a temperature value sensed in the system. In an embodiment,processing logic determines that a temperature value satisfies atemperature threshold. Responsive to determining that a temperaturevalue satisfies a temperature threshold, processing logic determines theattenuation coefficient used to generate the estimated noise signal. Forexample, processing device 116 may receive or generate a temperaturevalue indicative of the temperature of the electrode layer 106 or shieldlayer 108. The temperature value may exceed a predefined threshold ordrop below another predefined threshold, responsive to which processingdevice 116 executes method 1200 to determine a new attenuationcoefficient.

FIG. 13 is a block diagram illustrating an electronic system thatprocesses touch data, in accordance with aspects of the disclosure. FIG.13 illustrates an electronic system 1300 including a processing device1310 (which may be similar to processing device 116 described herein)that may be configured to measure capacitances from a sense array 1321(e.g., capacitive-sense array) with noise suppression module 1320, thesensor array 1321 forming a touch-sensing surface 1316. In oneembodiment, a multiplexer circuit may be used to connect acapacitance-sensing circuit 1301 with a sense array 1321. Thetouch-sensing surface 1316 (e.g., a touchscreen or a touch pad) iscoupled to the processing device 1310, which is coupled to a host 1350.In one embodiment, the touch-sensing surface 1316 is a two-dimensionalsense array (e.g., sense array 1321) that uses processing device 1310 todetect touches on the touch-sensing surface 1316.

In one embodiment, the sense array 1321 includes electrodes1322(1)-1322(N) (where N is a positive integer) that are disposed as atwo-dimensional matrix (also referred to as an XY matrix). The sensearray 1321 is coupled to pins 1313(1)-1313(N) of the processing device1310 via one or more analog buses 1315 transporting multiple signals. Insense array 1321, the first three electrodes (i.e., electrodes1322(1)-(3)) are connected to capacitance-sensing circuit 1301 and toground, illustrating a self-capacitance configuration. The lastelectrode (i.e., 1322(N)) has both terminals connected tocapacitance-sensing circuit 1301, illustrating a mutual capacitanceconfiguration. It should be noted that the other electrodes 1322 canhave both terminals connected to capacitance-sensing circuit 1301 aswell. In an alternative embodiment without an analog bus, each pin mayinstead be connected either to a circuit that generates a transmit ortransmission (TX) signal or to an individual receive (RX) sensorcircuit. The sense array 1321 may include a multi-dimension capacitivesense array. The multi-dimension sense array includes multiple senseelements, organized as rows and columns. In another embodiment, thesense array 1321 operates as an all-points-addressable (“APA”) mutualcapacitive sense array. The sense array 1321 may be disposed to have aflat surface profile. Alternatively, the sense array 1321 may havenon-flat surface profiles. Alternatively, other configurations ofcapacitive sense arrays may be used. For example, instead of verticalcolumns and horizontal rows, the sense array 1321 may have a hexagonarrangement, or the like. In one embodiment, the sense array 1321 may beincluded in an indium tin oxide (ITO) panel or a touch screen panel. Inone embodiment, sense array 1321 is a capacitive sense array. In anotherembodiment, the sense array 1321 is non-transparent capacitive sensearray (e.g., PC touchpad). In one embodiment, the sense array isconfigured so that processing device 1310 may generate touch data for atouch detected proximate to the capacitive sense array, the touch datarepresented as a plurality of cells.

In one embodiment, the capacitance-sensing circuit 1301 may include aCDC or other means to convert a capacitance into a measured value. Thecapacitance-sensing circuit 1301 may also include a counter or timer tomeasure the oscillator output. The processing device 1310 may furtherinclude software components to convert the count value (e.g.,capacitance value) into a touch detection decision or relativemagnitude. It should be noted that there are various known methods formeasuring capacitance, such as current versus voltage phase shiftmeasurement, resistor-capacitor charge timing, capacitive bridgedivider, charge transfer, successive approximation, sigma-deltamodulators, charge-accumulation circuits, field effect, mutualcapacitance, frequency shift, or other capacitance measurementalgorithms. It should be noted however, instead of evaluating the rawcounts relative to a threshold, the capacitance-sensing circuit 1301 maybe evaluating other measurements to determine the user interaction. Forexample, in the capacitance-sensing circuit 1301 having a sigma-deltamodulator, the capacitance-sensing circuit 1301 is evaluating the ratioof pulse widths of the output (i.e., density domain), instead of the rawcounts being over or under a certain threshold.

In another embodiment, the capacitance-sensing circuit 1301 includes aTX signal generator to generate a TX signal (e.g., stimulus signal) tobe applied to the TX electrode and a receiver (also referred to as a“sensing channel” or “receiving (Rx) channel” or “channel”), such as abuffer or an integrator, to measure an RX signal on the RX electrode. Insome embodiments, each Rx channel may be coupled to a physical pin ofprocessing device 1310 (or capacitance-sensing circuit 1301). In someembodiments, each Rx channel may include hardware such as a buffer or anintegrator. In a further embodiment, the capacitance-sensing circuit1301 includes an analog-to-digital converter (ADC) coupled to an outputof the receiver to convert the measured RX signal to a digital value.The digital value can be further processed by the processing device1310, the host 1350, or both.

The processing device 1310 is configured to detect one or more toucheson a touch-sensing device, such as the sense array 1321. The processingdevice can detect conductive obj ects, such as touch objects (fingers orpassive styluses, an active stylus, or any combination thereof). Thecapacitance-sensing circuit 1301 can measure a touch data on the sensearray 1321. The touch data may be represented as multiple cells, eachcell representing an intersection of sense elements (e.g., electrodes)of the sense array 1321. The capacitive sense elements are electrodes ofconductive material, such as copper, silver, indium tin oxide (ITO),metal mesh, carbon nanotubes, or the like. The sense elements may alsobe part of an ITO panel. The capacitive sense elements can be used toallow the capacitance-sensing circuit 1301 to measure self-capacitance,mutual capacitance, or any combination thereof. In another embodiment,the touch data measured by the capacitance-sensing circuit 1301 can beprocessed by the processing device 1310 to generate a 2D capacitiveimage of the sense array 1321 (e.g., capacitive-sense array). In oneembodiment, when the capacitance-sensing circuit 1301 measures mutualcapacitance of the touch-sensing device (e.g., capacitive-sense array),the capacitance-sensing circuit 1301 determines a 2D capacitive image ofthe touch-sensing object on the touch surface and processes the data forpeaks and positional information. In another embodiment, the processingdevice 1310 is a microcontroller that obtains a capacitance touch signaldata set, such as from a sense array, and finger detection firmwareexecuting on the microcontroller identifies data set areas that indicatetouches, detects and processes peaks, calculates the coordinates, or anycombination therefore. The firmware can calculate a precise coordinatefor the resulting peaks. In one embodiment, the firmware can calculatethe precise coordinates for the resulting peaks using a centroidalgorithm, which calculates a centroid of the touch, the centroid beinga center of mass of the touch. The centroid may be an X/Y coordinate ofthe touch. Alternatively, other coordinate interpolation algorithms maybe used to determine the coordinates of the resulting peaks. Themicrocontroller can report the precise coordinates to a host processor,as well as other information.

In one embodiment, the processing device 1310 further includesprocessing logic 1302. Some or all of the operations of the processinglogic 1302 may be implemented in firmware, hardware, or software or somecombination thereof. The processing logic 1302 may receive signals fromthe capacitance-sensing circuit 1301, and determine the state of thesense array 1321, such as whether an object (e.g., a finger) is detectedon or in proximity to the sense array 1321 (e.g., determining thepresence of the object), resolve where the object is on the sense array(e.g., determining the location of the object), tracking the motion ofthe object, or other information related to an object detected at thetouch sensor. In another embodiment, processing logic 1302 may includecapacitance-sensing circuit 1301.

The processing logic 1302 can be implemented in a capacitive touchscreen controller. In one embodiment, the capacitive touch screencontroller is the TrueTouch® capacitive controllers and CapSense®technology controllers (touch screens, buttons, sliders, proximity,etc.), such as the CY8C[2|3|4|5|6]xxxx family and CY8CMBRxx family ofCapSense controllers, developed by Cypress Semiconductor Corporation ofSan Jose, Calif. The CapSense® technology can be delivered as aperipheral function in the Programmable System on a Chip (PSoC®)processing device, developed by Cypress Semiconductor Corporation, SanJose, California, such as the PSoC® 1, 3, 4, 5, 6 devices. The CapSense®controllers' sensing technology can resolve touch locations of multiplefingers and a stylus on the touch-screens, supports operating systems,and is optimized for low-power multi-touch gesture and all-pointtouchscreen functionality. Alternatively, the touch position calculationfeatures may be implemented in other touchscreen controllers, or othertouch controllers of touch-sensing devices. In one embodiment, the touchposition calculation features may be implemented with other touchfiltering algorithms as would be appreciated by one of ordinary skill inthe art having the benefit of this disclosure.

In another embodiment, instead of performing the operations of theprocessing logic 1302 in the processing device 1310, the processingdevice 1310 may send the raw data or partially-processed data to thehost 1350. The host 1350, as illustrated in FIG. 13, may includedecision logic 1351 that performs some or all of the operations of theprocessing logic 1302. Noise suppression module 1320 may be implementedpartially or fully by decision logic 1351. Noise suppression module 1320may be a module within decision logic 1351. Alternatively, noisesuppression module 1320 may be an algorithm in decision logic 1351. Host1350 may obtain raw capacitance data from processing device 1310, anddetermine if a touch has occurred or not occurred on sense array 1321.Operations of the decision logic 1351 may be implemented in firmware,hardware, software, or a combination thereof. The host 1350 may includea high-level Application Programming Interface (API) in applications1352 that perform routines on the received data, such as compensatingfor sensitivity differences, other compensation algorithms, baselineupdate routines, start-up and/or initialization routines, interpolationoperations, or scaling operations. The operations described with respectto the processing logic 1302 may be implemented in the decision logic1351, the applications 1352, or in other hardware, software, and/orfirmware external to the processing device 1310. In some otherembodiments, the processing device 1310 is the host 1350.

In another embodiment, the processing device 1310 may also include anon-sensing actions block 1303. Non-sensing actions block 1303 may beused to process and/or receive/transmit data to and from the host 1350.For example, additional components may be implemented to operate withthe processing device 1310 along with the sense array 1321 (e.g.,keyboard, keypad, mouse, trackball, LEDs, displays, or other peripheraldevices).

As illustrated, capacitance-sensing circuit 1301 may be integrated intoprocessing device 1310. Capacitance-sensing circuit 1301 may include ananalog I/O for coupling to an external component, such as touch-sensorpad (not shown), sense array 1321, touch-sensor slider (not shown),touch-sensor buttons (not shown), and/or other devices. Thecapacitance-sensing circuit 1301 may be configurable to measurecapacitance using mutual-capacitance sensing techniques,self-capacitance sensing technique, charge coupling techniques,combinations thereof, or the like. In one embodiment,capacitance-sensing circuit 1301 operates using a charge accumulationcircuit, a capacitance modulation circuit, or other capacitance sensingmethods known by those skilled in the art. In an embodiment, thecapacitance-sensing circuit 1301 is of the Cypress controllers.Alternatively, other capacitance-sensing circuits may be used. Themutual capacitive sense arrays, or touch screens, as described herein,may include a transparent, conductive sense array disposed on, in, orunder either a visual display itself (e.g. LCD monitor), or atransparent substrate in front of the display. In an embodiment, the TXand RX electrodes are configured in rows and columns, respectively. Itshould be noted that the rows and columns of electrodes can beconfigured as TX or RX electrodes by the capacitance-sensing circuit1301 in any chosen combination. In one embodiment, the TX and RXelectrodes of the sense array 1321 are configurable to operate as TX andRX electrodes of a mutual capacitive sense array in a first mode todetect touch objects, and to operate as electrodes of a coupled-chargereceiver in a second mode to detect a stylus on the same electrodes ofthe sense array. The stylus, which generates a stylus TX signal whenactivated, is used to couple charge to the capacitive sense array,instead of measuring a mutual capacitance at an intersection of an RXelectrode and a TX electrode (including one or more sense element) asdone during mutual-capacitance sensing. An intersection between twosense elements may be understood as a location at which one senseelectrode crosses over or overlaps another, while maintaining galvanicisolation from each other. The capacitance associated with theintersection between a TX electrode and an RX electrode can be sensed byselecting every available combination of TX electrode and RX electrode.When a touch object (i.e., conductive object), such as a finger orstylus, approaches the sense array 1321, the touch object causes adecrease in mutual capacitance between some of the TX/RX electrodes. Inanother embodiment, the presence of a finger increases the couplingcapacitance of the electrodes. Thus, the location of the finger on thesense array 1321 can be determined by identifying the RX electrodehaving a decreased coupling capacitance between the RX electrode and theTX electrode to which the TX signal was applied at the time thedecreased capacitance was measured on the RX electrode. Therefore, bysequentially determining the capacitances associated with theintersection of electrodes, the locations of one or more inputs can bedetermined. It should be noted that the process can calibrate the senseelements (intersections of RX and TX electrodes) by determiningbaselines for the sense elements. It should also be noted thatinterpolation may be used to detect finger position at betterresolutions than the row/column pitch as would be appreciated by one ofordinary skill in the art. In addition, various types of coordinateinterpolation algorithms may be used to detect the center of the touchas would be appreciated by one of ordinary skill in the art.

It should also be noted that the embodiments described herein are notlimited to having a configuration of a processing device coupled to ahost, but may include a system that measures the capacitance on thesensing device and sends the raw data to a host computer where it isanalyzed by an application. In another embodiment, the processing thatis done by processing device 1310 is done in the host.

The processing device 1310 may reside on a common carrier substrate suchas, for example, an integrated circuit (IC) die substrate, or amulti-chip module substrate. Alternatively, the components of theprocessing device 1310 may be one or more separate integrated circuitsand/or discrete components. In one embodiment, the processing device1310 may be the Programmable System on a Chip (PSoC®) processing device,developed by Cypress Semiconductor Corporation, San Jose, Calif. Oneembodiment of the PSoC® processing device is illustrated and describedbelow with respect to FIG. 14. Alternatively, the processing device 1310may be one or more other processing devices known by those of ordinaryskill in the art, such as a microprocessor or central processing unit, acontroller, special-purpose processor, digital signal processor (DSP),an application specific integrated circuit (ASIC), a field programmablegate array (FPGA), or other programmable device. In an alternativeembodiment, for example, the processing device 1310 may be a networkprocessor having multiple processors including a core unit and multiplemicro-engines. Additionally, the processing device 1310 may include anycombination of general-purpose processing device(s) and special-purposeprocessing device(s).

Capacitance-sensing circuit 1301 may be integrated into the IC of theprocessing device 1310, or alternatively, in a separate IC.Alternatively, descriptions of capacitance-sensing circuit 1301 may begenerated and compiled for incorporation into other integrated circuits.For example, behavioral level code describing the capacitance-sensingcircuit 1301, or portions thereof, may be generated using a hardwaredescriptive language, such as VHDL or Verilog, and stored to amachine-accessible medium (e.g., CD-ROM, hard disk, floppy disk, etc.).Furthermore, the behavioral level code can be compiled into registertransfer level (“RTL”) code, a netlist, or even a circuit layout andstored to a machine-accessible medium. The behavioral level code, theRTL code, the netlist, and the circuit layout may represent variouslevels of abstraction to describe capacitance-sensing circuit 1301.

It should be noted that the components of electronic system 1300 mayinclude all the components described above. Alternatively, electronicsystem 1300 may include some of the components described above.

In one embodiment, the electronic system 1300 is used in a tabletcomputer. Alternatively, the electronic device may be used in otherapplications, such as a notebook computer, a mobile handset, a personaldata assistant (“PDA”), a keyboard, a television, a remote control, amonitor, a handheld multi-media device, a handheld media (audio and/orvideo) player, a handheld gaming device, a signature input device forpoint of sale transactions, an eBook reader, global position system(“GPS”) or a control panel, among others. The embodiments describedherein are not limited to touch screens or touch-sensor pads fornotebook implementations, but can be used in other capacitive sensingimplementations, for example, the sensing device may be a touch-sensorslider (not shown) or touch-sensor buttons (e.g., capacitance sensingbuttons). In one embodiment, these sensing devices include one or morecapacitive sensors or other types of capacitance-sensing circuitry. Theoperations described herein are not limited to notebook pointeroperations, but can include other operations, such as lighting control(dimmer), volume control, graphic equalizer control, speed control, orother control operations requiring gradual or discrete adjustments. Itshould also be noted that these embodiments of capacitive sensingimplementations may be used in conjunction with non-capacitive sensingelements, including but not limited to pick buttons, sliders (ex.display brightness and contrast), scroll-wheels, multi-media control(ex. volume, track advance, etc.) handwriting recognition, and numerickeypad operation.

Electronic system 1300 includes capacitive button 1323. Capacitivebutton 1323 is connected to processing device 1310. In one embodiment,capacitive button 1323 may be a single electrode. In another embodiment,capacitive button 1323 may be a pair of electrodes. In one embodiment,capacitive button 1323 is disposed on a substrate. In one embodiment,capacitive button 1323 may be part of sense array 1321. In anotherembodiment, capacitive button may be a separate from sense array 1321.In one embodiment, capacitive button 1323 may be used to inself-capacitance scan mode. In another embodiment, capacitive button1323 may be used in mutual capacitance scan mode. In one embodiment,capacitive button 1323 may be used in both self-capacitance scan modeand mutual capacitance scan mode. Alternatively, the capacitive button1323 is used in a multi-stage capacitance measurement process asdescribed herein. Capacitive button 1323 may be one or more distinctbuttons.

FIG. 14 illustrates an embodiment of a core architecture 1400 of thePSoC® processing device, such as that used in the PSoC3® family ofproducts offered by Cypress Semiconductor Corporation (San Jose,Calif.). In one embodiment, the core architecture 1400 includes amicrocontroller 1402. The microcontroller 1402 includes a CPU (centralprocessing unit) core 1404, flash program storage 1406, DOC (debug onchip) 1408, a prefetch buffer 1410, a private SRAM (static random accessmemory) 1412, and special functions registers 1414. In an embodiment,the DOC 1408, prefetch buffer 1410, private SRAM 1412, and specialfunction registers 1414 are coupled to the CPU core 1404, while theflash program storage 1406 is coupled to the prefetch buffer 1410.

The core architecture 1400 may also include a CHub (core hub) 1416,including a bridge 1418 and a direct memory access (DMA) controller 1420that is coupled to the microcontroller 1402 via bus 1422. The CHub 1416may provide the primary data and control interface between themicrocontroller 1402 and its peripherals (e.g., peripherals) and memory,and a programmable core 1424. The DMA controller 1420 may be programmedto transfer data between system elements without burdening the CPU core1404. In various embodiments, each of these subcomponents of themicrocontroller 1402 and CHub 1416 may be different with each choice ortype of CPU core 1404. The CHub 1416 may also be coupled to shared SRAM1426 and an SPC (system performance controller) 1428. The private SRAM1412 is independent of the shared SRAM 1426 that is accessed by themicrocontroller 1402 through the bridge 1418. The CPU core 1404 accessesthe private SRAM 1412 without going through the bridge 1418, thusallowing local register and RAM accesses to occur simultaneously withDMA access to shared SRAM 1426. Although labeled here as SRAM, thesememory modules may be any suitable type of a wide variety of (volatileor non-volatile) memory or data storage modules in various otherembodiments.

In various embodiments, the programmable core 1424 may include variouscombinations of subcomponents (not shown), including, but not limitedto, a digital logic array, digital peripherals, analog processingchannels, global routing analog peripherals, DMA controller(s), SRAM andother appropriate types of data storage, IO ports, and other suitabletypes of subcomponents. In one embodiment, the programmable core 1424includes a GPIO (general purpose IO) and EMIF (extended memoryinterface) block 1430 to provide a mechanism to extend the externaloff-chip access of the microcontroller 1402, a programmable digitalblock 1432, a programmable analog block 1434, and a special functionsblock 1436, each configured to implement one or more of the subcomponentfunctions. In various embodiments, the special functions block 1436 mayinclude dedicated (non-programmable) functional blocks and/or includeone or more interfaces to dedicated functional blocks, such as USB, acrystal oscillator drive, JTAG, and the like.

The programmable digital block 1432 may include a digital logic arrayincluding an array of digital logic blocks and associated routing. Inone embodiment, the digital block architecture is comprised of UDBs(universal digital blocks). For example, each UDB may include an ALUtogether with CPLD functionality.

In various embodiments, one or more UDBs of the programmable digitalblock 1432 may be configured to perform various digital functions,including, but not limited to, one or more of the following functions: abasic I2C slave; an I2C master; a SPI master or slave; a multi-wire(e.g., 3-wire) SPI master or slave (e.g., MISO/MOSI multiplexed on asingle pin); timers and counters (e.g., a pair of 8-bit timers orcounters, one 16 bit timer or counter, one 8-bit capture timer, or thelike); PWMs (e.g., a pair of 8-bit PWMs, one 16-bit PWM, one 8-bitdeadband PWM, or the like), a level sensitive I/O interrupt generator; aquadrature encoder, a UART (e.g., half-duplex); delay lines; and anyother suitable type of digital function or combination of digitalfunctions which can be implemented in a plurality of UDBs.

In other embodiments, additional functions may be implemented using agroup of two or more UDBs. Merely for purposes of illustration and notlimitation, the following functions can be implemented using multipleUDBs: an I2C slave that supports hardware address detection and theability to handle a complete transaction without CPU core (e.g., CPUcore 1404) intervention and to help prevent the force clock stretchingon any bit in the data stream; an I2C multi-master which may include aslave option in a single block; an arbitrary length PRS or CRC (up to 32bits); SDIO; SGPIO; a digital correlator (e.g., having up to 32 bitswith 4× over-sampling and supporting a configurable threshold); a LINbusinterface; a delta-sigma modulator (e.g., for class D audio DAC having adifferential output pair); an I2S (stereo); an LCD drive control (e.g.,UDBs may be used to implement timing control of the LCD drive blocks andprovide display RAM addressing); full-duplex UART (e.g., 7-, 8- or 9-bitwith 1 or 2 stop bits and parity, and RTS/CTS support), an IRDA(transmit or receive); capture timer (e.g., 16-bit or the like);deadband PWM (e.g., 16-bit or the like); an SMbus (including formattingof SMbus packets with CRC in software); a brushless motor drive (e.g.,to support 6/12 step commutation); auto BAUD rate detection andgeneration (e.g., automatically determine BAUD rate for standard ratesfrom 1200 to 115200 BAUD and after detection to generate required clockto generate BAUD rate); and any other suitable type of digital functionor combination of digital functions which can be implemented in aplurality of UDBs.

The programmable analog block 1434 may include analog resourcesincluding, but not limited to, comparators, mixers, PGAs (programmablegain amplifiers), TIAs (trans-impedance amplifiers), ADCs(analog-to-digital converters), DACs (digital-to-analog converters),voltage references, current sources, sample and hold circuits, and anyother suitable type of analog resources. The programmable analog block1434 may support various analog functions including, but not limited to,analog routing, LCD drive IO support, capacitance-sensing, voltagemeasurement, motor control, current to voltage conversion, voltage tofrequency conversion, differential amplification, light measurement,inductive position monitoring, filtering, voice coil driving, magneticcard reading, acoustic doppler measurement, echo-ranging, modemtransmission and receive encoding, or any other suitable type of analogfunction.

In an embodiment, programmable core 1424 may include noise suppressionmodule 1320 to perform one or more aspects of the disclosure. Some areall of component or operations of noise suppression module 1320 may beperformed by one or more of the subcomponents of programmable core 1424.It can be noted that other components of core architecture 1400 mayperform some or all of the operations of noise suppression module 1320or include some or all the components used by noise suppression module1320.

The embodiments described herein may be used in various designs ofmutual-capacitance sensing systems, in self-capacitance sensing systems,or combinations of both. In one embodiment, the capacitance sensingsystem detects multiple sense elements that are activated in the arrayand can analyze a signal pattern on the neighboring sense elements toseparate noise from actual signal. The embodiments described herein arenot tied to a particular capacitive sensing solution and can be used aswell with other sensing solutions, including optical sensing solutions,as would be appreciated by one of ordinary skill in the art having thebenefit of this disclosure.

In the above description, numerous details are set forth. It will beapparent, however, to one of ordinary skill in the art having thebenefit of this disclosure, that embodiments of the present disclosuremay be practiced without these specific details. In some instances,well-known structures and devices are shown in block diagram form,rather than in detail, in order to avoid obscuring the description.

Some portions of the detailed description are presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared and otherwise manipulated. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as “measuring,” “generating,” “subtracting,” “buffering,”“integrating,” “multiplying,” “determining,” “causing,” “setting,”“estimating,” or the like, refer to the actions and processes of acomputing system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (e.g.,electronic) quantities within the computing system's registers andmemories into other data similarly represented as physical quantitieswithin the computing system memories or registers or other suchinformation storage, transmission or display devices.

The words “example” or “exemplary” are used herein to mean serving as anexample, instance, or illustration. Any aspect or design describedherein as “example’ or “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe words “example” or “exemplary” is intended to present concepts in aconcrete fashion. As used in this application, the term “or” is intendedto mean an inclusive “or” rather than an exclusive “or.” That is, unlessspecified otherwise, or clear from context, “X includes A or B” isintended to mean any of the natural inclusive permutations. That is, ifX includes A; X includes B; or X includes both A and B, then “X includesA or B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Moreover, use of the term “an embodiment” or “one embodiment” or“an implementation” or “one implementation” throughout is not intendedto mean the same embodiment or implementation unless described as such.

Embodiments descried herein may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. Such a computer program may bestored in a non-transitory computer-readable storage medium, such as,but not limited to, any type of disk including floppy disks, opticaldisks, CD-ROMs and magnetic-optical disks, read-only memories (ROMs),random access memories (RAMs), EPROMs, EEPROMs, magnetic or opticalcards, flash memory, or any type of media suitable for storingelectronic instructions. The term “computer-readable storage medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database and/or associated caches andservers) that store one or more sets of instructions. The term“computer-readable medium” shall also be taken to include any mediumthat is capable of storing, encoding, or carrying a set of instructionsfor execution by the machine and that causes the machine to perform anyone or more of the methodologies of the present embodiments. The term“computer-readable storage medium” shall accordingly be taken toinclude, but not be limited to, solid-state memories, optical media,magnetic media, any medium that is capable of storing a set ofinstructions for execution by the machine and that causes the machine toperform any one or more of the methodologies of the present embodiments.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present embodiments are not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the embodiments as described herein.

The above description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent disclosure. It will be apparent to one skilled in the art,however, that at least some embodiments of the present disclosure may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present embodiments. Thus, the specific details set forth above aremerely exemplary. Particular implementations may vary from theseexemplary details and still be contemplated to be within the scope ofthe present embodiments.

It is to be understood that the above description is intended to beillustrative and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the embodiments should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A method comprising: measuring, at a firstchannel of a processing device, a first signal indicative a touch objectproximate to an electrode layer, the first signal comprising a touchdata component and a first noise component generated by a noise source;measuring, at a second channel of the processing device, a second signalcomprising a second noise component generated by the noise source,wherein the second channel is coupled to a shield layer disposed betweenthe noise source and the electrode layer; generating an estimated noisesignal using the second noise component of the second signal that isassociated with the second channel, wherein the estimated noise signalis an estimation of the first noise component of the first signal; andsubtracting the estimated noise signal from the measured first signal toobtain the touch data component of the first signal.
 2. The method ofclaim 1, wherein measuring the first signal at the first channel isperformed concurrently with measuring the second signal at the secondchannel.
 3. The method of claim 1, wherein measuring the first signalindicative of the touch object proximate to the electrode layercomprises: buffering the first signal using first buffer of the firstchannel; and integrating the buffered first signal; and whereinmeasuring the second signal comprising the second noise componentgenerated by the noise source comprises: buffering the second signalusing a second buffer of the second channel; and integrating thebuffered second signal.
 4. The method of claim 1, wherein generating theestimated noise signal using the second noise component of the secondsignal that is associated with the second channel comprises: attenuatingthe second signal by an attenuation coefficient to generate theestimated noise signal.
 5. The method of claim 1, further comprising:determining an attenuation coefficient used to generate the estimatednoise signal.
 6. The method of claim 5, further comprising: determiningthat a temperature value satisfies a temperature threshold, whereindetermining the attenuation coefficient used to generate the estimatednoise signal is performed responsive to determining that the temperaturevalue satisfies the temperature threshold.
 7. The method of claim 5,wherein determining the attenuation coefficient used to generate theestimated noise signal comprises: determining that the noise source ispowered on; setting the attenuation coefficient to a predeterminedvalue; measuring, at the first channel of the processing device, a thirdsignal comprising a third noise component; measuring, at the secondchannel of the processing device, a fourth signal comprising a fourthnoise component; and estimating the attenuation coefficient using thethird signal and the fourth signal.
 8. The method of claim 1, whereinthe noise source generates a noise signal comprising the first noisecomponent and the second noise component.
 9. The method of claim 1,wherein the noise source comprises a display device.
 10. The method ofclaim 1, wherein the first channel is coupled to the electrode layer.11. A processing device, comprising: a first channel to measure a firstsignal indicative of a touch object proximate to an electrode layer, thefirst signal comprising a touch data component and a first noisecomponent generated by a noise source; and a second channel to measure asecond signal comprising a second noise component generated by the noisesource, wherein the second channel is coupled to a shield layer disposedbetween the noise source and the electrode layer; and wherein theprocessing device to: generate an estimated noise signal using thesecond noise component of the second signal associated with the secondchannel, wherein the estimated noise signal is an estimation of thefirst noise component of the first signal; and subtract the estimatednoise signal from the measured first signal to obtain the touch datacomponent of the first signal.
 12. The processing device of claim 11,wherein the first channel and the second channel to concurrently measurethe first signal and the second signal respectively.
 13. The processingdevice of claim 11, wherein to generate the estimated noise signal usingthe second noise component of the second signal associated with thesecond channel, the processing device to: attenuate the second signal byan attenuation coefficient to generate the estimated noise signal. 14.The processing device of claim 11, the processing device further todetermine an attenuation coefficient used to generate the estimatednoise signal, wherein to determine the attenuation coefficient theprocessing device to: determine that the noise source is powered on; setthe attenuation coefficient to a predetermined value; measure, at thefirst channel of the processing device, a third signal comprising athird noise component; measure, at the second channel of the processingdevice, a fourth signal comprising a fourth noise component; andestimate the attenuation coefficient using the third signal and thefourth signal.
 15. The processing device of claim 11, wherein the noisesource comprises a display device.
 16. A system, comprising: a displaydevice to generate a noise signal comprising a first noise component anda second noise component; a shield layer disposed above the displaydevice; an electrode layer disposed above the shield layer; and aprocessing device comprising: a first channel coupled to the electrodelayer, the first channel to measure a first signal indicative of a touchobject proximate to the electrode layer, the first signal comprising atouch data component and the first noise component generated by thedisplay device; and a second channel coupled to the shield layer, thesecond channel to measure a second signal comprising the second noisecomponent generated by the display device; and wherein the processingdevice to: generate an estimated noise signal using the second noisecomponent of the second signal associated with the second channel,wherein the estimated noise signal is an estimation of the first noisecomponent of the first signal; and subtract the estimated noise signalfrom the measured first signal to obtain the touch data component of thefirst signal.
 17. The system of claim 16, further comprising: acapacitor coupled in series with the second channel and the shieldlayer.
 18. The system of claim 17, further comprising: a resistorcomprising: a first terminal coupled between the shield layer and thesecond channel; and a second terminal coupled to a ground potential. 19.The system of claim 18, wherein at least one of the capacitor orresistor is integrated into the processing device.
 20. The system ofclaim 16, wherein to measure the first signal indicative of the touchobject proximate to the electrode layer, the first channel comprises: afirst buffer to buffer the first signal; and a first integrator tointegrate the buffered first signal; and wherein to measure the secondsignal comprising the second noise component generated by the displaydevice, the second channel comprises: a second buffer to buffer thesecond signal; and a second integrator to integrate the buffered secondsignal.